<?php

    require 'facebook.php';

// Create our Application instance (replace this with your appId and secret).
    $facebook = new Facebook(array(
        'appId' => FACEBOOK_APP_ID,
        'secret' => FACEBOOK_SECRET_ID,
    ));

// Get User ID
    $user = $facebook->getUser();

// We may or may not have this data based on whether the user is logged in.
//
// If we have a $user id here, it means we know the user is logged into
// Facebook, but we don't know if the access token is valid. An access
// token is invalid if the user logged out of Facebook.

    if ($user)
    {
        try
        {
            // Proceed knowing you have a logged in user who's authenticated.
            $user_profile = $facebook->api('/me');
        }
        catch (FacebookApiException $e)
        {
            error_log($e);
            $user = null;
        }
    }

// Login or logout url will be needed depending on current user state.
    if ($user)
    {
        $logoutUrl = $facebook->getLogoutUrl();
    }
    else
    {
        $loginUrl = $facebook->getLoginUrl();
    }
?>